Related Experiment Video
Updated: May 16, 2026
09:00
Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
Published on: June 28, 2018
Why is the bulk resistivity of topological insulators so small?
Brian Skinner1, Tianran Chen, B I Shklovskii
1Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Physical Review Letters
|December 11, 2012
Summary
Topological insulators (TIs) exhibit low bulk resistivity due to band bending from Coulomb potential fluctuations. Numerical simulations confirm this, showing an activation energy consistent with experimental data for compensated TIs.
Area of Science:
- Condensed matter physics
- Materials science
Background:
- As-grown topological insulators (TIs) are typically n-type doped.
- Compensation aims to shift the Fermi level but results in low bulk resistivity.
Purpose of the Study:
- Investigate the cause of low bulk resistivity in topological insulators.
- Explain the role of band bending and Coulomb potential fluctuations.
Main Methods:
- Numerical simulations of a completely compensated TI model.
- Analysis of bulk resistivity and transport mechanisms.
Main Results:
- Identified band bending from poorly screened Coulomb potential fluctuations as the cause.
- Calculated bulk resistivity activation energy of 0.15 times the band gap.
- Observed crossover to variable range hopping at lower temperatures.
Conclusions:
- Band bending significantly impacts bulk resistivity in TIs.
- Simulation results align with experimental observations.
- Variable range hopping with large localization length dominates at low temperatures.
Related Concept Videos
01:22Resistivity
When a voltage is applied to a conductor, an electrical field is generated, and charges in the conductor feel the force due to the electrical field. The current density that results depends on the electrical field and the properties of the material. In some materials, including metals at a given temperature, the current density is approximately proportional to the electrical field. In these cases, the current density can be modeled as:
01:22Semiconductors
There is variation in the electrical conductivity of materials - metals, semiconductors, and insulators that are showcased with the help of the energy band diagrams.
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
02:35Band Theory
When two or more atoms come together to form a molecule, their atomic orbitals combine and molecular orbitals of distinct energies result. In a solid, there are a large number of atoms, and therefore a large number of atomic orbitals that may be combined into molecular orbitals. These groups of molecular orbitals are so closely placed together to form continuous regions of energies, known as the bands.
The energy difference between these bands is known as the band gap.
Conductor, Semiconductor,...
The energy difference between these bands is known as the band gap.
Conductor, Semiconductor,...
01:13Electrical Conductivity
In perfect conductors, the electric field inside is always zero due to the abundance of free electrons, which nullify any field by flowing. As a result, any residual charge resides on the surface.
In a practical conductor, an applied electric field may be sustained, causing a flow of electrons, which produce a current. The differential form of the current, the current density, is related to the electric field.
More generally, it is related to the force per unit charge, which involves the...
In a practical conductor, an applied electric field may be sustained, causing a flow of electrons, which produce a current. The differential form of the current, the current density, is related to the electric field.
More generally, it is related to the force per unit charge, which involves the...
01:24Superconductor
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a superconductor. In 1911, Heike Kamerlingh Onnes of Leiden University, a Dutch physicist, observed a relation between the temperature and the resistance of the element mercury. The mercury sample was then cooled in liquid helium to study the linear dependence of resistance on temperature. It was observed that, as the temperature decreased, the...
01:28Types Of Superconductors
A superconductor is a substance that offers zero resistance to the electric current when it drops below a critical temperature. Zero resistance is not the only interesting phenomenon as materials reach their transition temperatures. A second effect is the exclusion of magnetic fields. This is known as the Meissner effect. A light, permanent magnet placed over a superconducting sample will levitate in a stable position above the superconductor. High-speed trains that levitate on strong...